Honing machine for piston pin holes



June 13, 1933.

J. SUNNEN HONING MACHINE F'OR PISTON PIN HOLES Filed Deo. 4, 1931 4 Sheets-Sheet l 11e/zi June 13, 1933. J. sUNNEN 1,913,689

HONING MACHINE FOR PISTON PIN HOLES,

Filed Deo. 4, 1931 4 Sheets-Sheet 2 N f/ d 77 l/ Eme/512W f4 dany/'0 .iam/m June 13, 1933. J. SUNNENy HONING MACHINE FOR PISTON PIN HOLES Filed Deo. 4, 195i 4 SheetSLSheet C? June-13, 1933- J. sUNNEN HONING MACHINE FOR PISTON PIN HOLES Filed Deo. 4, 1931 4 Sheets-Sheet 4 Patented June 13, 1933 PATENT OFFICE JOSEPH SUNNEN, 0F KIRKWOOD, MISSOURI KONING MACHINE FOR PISTON PIN HOLES Application led December 4, 1931. Serial No. 578,923.'

My invention has relation to improvements in grinding machines adapted for use in refinishing small sized bores, such as wrist piii holes and similar small bearings common in 5 internal combustion engines. The machine is akin to a reamer, although it operates primarily by abrasive action rather than shearing action, and it consists in the novel fea` tures of construction more fully set forth in the specification .and pointed out in the claims.

The invention is primarily for the pury pose of reboring small holes to receive new pins, for which reason it is essential that the tool holder be so designed as to employ great relative strength and rigidity comparative to the. size thereof. It is, therefore, the object of the present invention to provide a pin hole grinder having an abrasive element rigidly carried on a rotatable spindle, or mandrel, that is adapted to traverse the hole being ground; one in which the spindle, although supported only at one end, possesses the degree of rigidity essential to produce a true cylindrical hole, one in which the abrasive element is adjustably mounted inthe mandrel in order to adapt the grinder to different sizes of pin holes so that one tool may be made to perform the grindin operation on a Wide `range of holes; one w ich operates with a minimum amount of vibration; one in which fixed guide elements are provided to cooperate with the abrasive element and confixed orbitI for any adjustment, thereb insuring the production of a cylindrical liole; one embodying means for causing the grinding element to adhere tothe surface being ground without chatteringgand one in which the guide elements of the tool are composed of a suitable'metallic alloy so that they will have a relatively long life and will Wear substantially uniformly throughout their entire extent.

single abrasive element andthus avoid excessive weakening of the mandrel by providing a plurality of grooves :for receiving the abrasive elements.- This feature is iinine the rotation of the same to a substantially It is also an advantage to employ but av portant on account of the small diameter of' the mandrel necessary to operate on pin holes of small diameter,such as Wrist pin holes.

It is a further object of the invention to form the guide elements integrally with the to ol holder, or mandrel, as a matter of simplicity and economy of manufacture, and at the same time constituting the holder of ai material that will embody the requisite strength and rigidity essential to it, which material at the same time embodies properties essential to the satisfactory performance of the guide elements. I have discovered that one mater1al, possessing the properties' essential both to the guide elements and the tool holder, consists of `a zinc alloy containing both aluminum and copper. i

Further objects of the invention are to provide a horizontally disposed revoluble member or mandrel having a longitudinally disposed .groove .formed therein and provided with a plurality of longitudinally disposed radially projecting ribs arranged in spaced i peripheral relation -With said groove, there f being an adjustable blade longitudinally disposed in said groove having an obliquely disposed portion, and a mount or shoe movably disposed in said groove and engaging said obli ue portion and carrying onits outer face an a rasive stick Wherebythe adjusting longitudinal movement of said blade causes radial movement of said abrasive stick, said longitudinal ribs forming .non-abrasive points of engagement 'with the cylinder surface operated upon and serving to steady said revoluble member during the operation thereof.

`Additional objectsof the invention are tot v provide a bearing member adapted to be stationarily mounted, said bearing member having a horizontally disposed bearing in which is journaled a revoluble memberf or mandrel provided with cylinder engaging elements, said member being provided with bearings spaced from the first bearing and having journaled therein a rock shaft carrying an electric portable drill which is engageable with the revoluble member so as to actuate the latter, said rock shaft being operable to bring said drill into and out of operative engagement with said revoluble member.

i 15 means in disengaged position.

With these and other objects in view, my invention consists in certain novel features of construction and arrangement of parts, hereinafter more fully described and claimed,

and illustrated in the accompanying drawing?, in whichv igure 1 is a top plan view of my piston V .pin hole grinding machine, showing the driv- 1n means engaged with the mandrel ortool ho der.

Figure 2 is a vertical cross section taken on line 2--2 of Figure 1. v N.

Figure 3 is a vertical cross section taken on line 3-3 of Figure 1, showing the driving Figure 4 is a lon itudihal cross section taken on line 4-4 of igure 1.

Figure 5 is an enlarged vertical cross section taken on line 5-5 of Figure 4. 0 Figure 6 is a vertical cross section taken on line 6-6 of Figure 4.

Figure 7 is avertical cross section taken on line 7-7 of Figure 4.

Figure 8 is a vertical longitudinalsectlon 6 taken on line 8-8 of Figure 4.

Figure 9 is a vertical cross section taken on line 9-9 of Figure 2.

Figure 10 is a vertical cross sectlon taken on line 10-10 of Figure 1.

I0 Figure 11 is a vertical cross section taken on line 11-11 of Figure 10.

Referring by numerals to the accompanying drawings, 10 indicates a bench on wh1c h rests a base 11. The upper end of whlch 1sv "85'- provided with a horizontally disposed wall 12 having a central aperture 14. A bearing member or casting 15 -is provided with a downwardly presented tubular extension 16 which rests on wall 12. A bolt 17 extends A0. through the a ertured top wall of member -15 and throug the aperture 14 and has its lower end engaging said bench lor support 10 while the upper end 17a of said bolt 1sl screw-threaded and receives a nut 175 wheres 43" by said casting or member 15. can be clamped securely in position on the base 11. l

, Casting 15 is disposed substantially 1n the horizontal plane 'above said base 11, and

terminates at its forward end in a horizon- 50- tally disposed tubular member 18 which forms a journal for a mandrel structure 19, hereinafter more fully described. The other end, which is preferably disposed slightly below the horizontal plane of member 18, terminates in a pair of spaced coaxial lugs 20, 20 in which is ournaled la rock shaft 21. This shaft is pre erabl rectangular in cross section and has the ower end 22 of a bearing member 24, mounted on it between lugs 20. 80S The upper end 25 of this-bearing member forms a 'ournal for a driver spindle 26, the outer endI of which is'reduced, and has mounted thereon a driver disk 27. This driver disk, which may be of any desired construction, is 65 preferably formed with a peripheral groove which is adapted frictionally to engage a driven disk 28 mounted on the mandrel structure 19 adjacent to the corresponding end of member l Normally bearing member 24 occupies a position shown in Figure 3 wherein the driver disk 27 is disengaged from the driven disk 28. The bearing member 24 has a downwardly projecting lug 29 formed integral withl it, in which one end of a rod 3() is secured. The other end of this rod terminates past the front edge of bench 10 andis pivotally connected at 31 to a treadle 32.A By pressing on said treadle, journal member 24 is rocked forwardly to bring the driver disk 27 into operative engagement with the driven disk 28, as shown in Figure 2. When the pressure is removed, journal member 24 moves to its normal or disengaged position shown in Figure 3, under the influence of a coiled spring 34. y

The driver s indle 26 is provided at one end with a head) 35 having an axial bore 35a and a diametrically disposed slot 355. A driver shank 36 is adapted to be secured in a chuck 37 of an electric hand drill 38 and has its outer end formed with an enlargement 'the driver spindle 26. The enlargement 36a is slightly tapered toward both ends to permit loose it thereof in said bore 35a and the pin 39'has a loose fit in said slot 35?). 'This arrangement allows driving engagement of Athe drill with the drivers spindle 26 without requiring said drill to be in perfect axial alignment therewith.

The drill 38 is supported in position by a socket 40 which latter is slidably mounted on the projecting end of rock shaft 21. The socket is vertically disposed to one side of said bar (see Figs 10 and 11) and receives the usual tubular portions or handle 38. which extends diametrically from said drill so that said ldrill rests on the upper end of said socket. This socket is formedwith an extension 40a which is arranged to one side of said socket and is provided with a horizontally disposed hole 41 in which the bar 21 is received. Preferably this hole is formed tapered at one end, as shown Yin Figure 11, so that said drill can adjust itself and is not rigidly held in position.

Thus when the journal member 24 is rocked, bar 21 is rocked therewith, thereby causing drill 38 to move substantially in coaxial alignment with the driver spindle 26. This arrangement permits easy attachment and detachment of the drill asby shifting the socket member 40 away from the journal bearing 24 drill 38 and the driver shank 36 are moved away from driver spindle 26,

structure comp'rises a driven spindleV V44V journaled in bearing 18 and having its ends extending past the ends of the latter. Y One of said ends is reduced in diameter as 'indicated at 44a and is screw-threaded to receive '15 a hub 28a"of driven `disk 28. A short shaft- 45 extends through', the reduced end 44a. The inner end of said shaft is provided with ahead'46 which'is loosely held in a seat 47 i formed in` spindle 44 for this purpose.

Theprojecting portion of said shaft is tapared, as indicated at 48, to receive the ta- -pered bore of a knurled adjusting member or knob 49. The end of the shaft is threaded and receives a nut by means of which knob 49 is held in position.

The opposite end of driven spindle 44 is formed with a tubular head 51 which is provided With an external screw-thread for receiving a coupling 52. This coupling has a lradialflange 52a which bears against head 42a of mandrel 42 and thus holds the latter securely in position against the threaded externally screw-threaded head 5l of the driven spindle 44 and in axial alignment therewith.

ln order to eliminate driving stresses from the coupling and the coupling members 52 and 42a 4and in order to insure efficient driving connection between the tubular spindle 44 and mandrel 42, the head42a ofthe latter is provided with an outwardly presented longitudinally disposed lug 55 whichiits into a longitudinally disposed groove 56 4'formed in the tubular head or enlargement The mandrel 42 is of a comparatively small diameter Iso as to t small-sized bores. This mandrel Iis provided with a longitudinal groove 57 which is closed near the outer end thereof, as indicated at-58. ,Said groove eiz-1V gIO 'tends thrcugh said mandrel; andffthrough thehead 42`tt `and opens into vsaid ytubular 4spindle 44. A cylinder engaging element or Y. hone shoe 58, having an abrasive element 59, is'mounted in this slot and projects radially therefrom. Mandrel 42 is provided with a pair of longitudinally disposed ribs or nonabrasive elements 60 which are preferably formed integral therewith and extend therefrom at points spaced peripherally from said Thus the inner surface of a cylinder or bore is engaged by an abrasive element at one element 59. These ribs are substantially co-4 point only and is engaged non-abrasiveL elements at two points spaced from'each other and from the abrasive element. These non-abrasive elements orribs 460. `serve to maintain the' mandrel 42 in proper alignment in the bore and to stead the ftool so Aas to prevent chattering or binding thereof when in use. e.

The abrasive element 59is secured in any suitable manner 'in shoe 58 and cthe latter is ofjsuiilcient depth so as to haveample bear.

ing surface with the' sides of the groove 57.

One side of shoe 58is cut away,` as indicated at 58a, so as to accommodate a wedge62 which is slidably arranged in said oove to one side thereof. The top wall vo the cutaway portion is disposed obliquely relatively 'to the longitudinal axis of the mandrel and the top 62a of the blade is correspondingly mclined. f

Blade 62 is movably arranged ingroove 57 and is pivotally connected to an adjusting member 64, as indicated at 65. f This adjusting member extends inwardly throughthe end 42a of mandrel 42 into tubular spindle44 and has its inner end terminating in a boss 66 which is provided with a screw-threaded opening 67. Engaging this opening is an adjusting screw 68 disposed longitudinally in said driven spindle 44. This screw is provided with an enlargement 69 which fits into the recess 47 formed in head 46 of adjusting shaft 45. This enlargement is tapered toward each end to permit :a-'slight'angular movement df the adjustingscrew relatively to said adjusting shaft. "i

A pin 70 extends diametrically through enlargement 6Land through head 46 and Vforms a universal joint therebetween. As

shown in Figure 8, the ends of this pin are "seated in head 46 and the medial portionlof said pin. is tapered to permit slight oblique movement of said adjusting screw 4relatively to said pin. v

By turning knob or adjusting member 49 in the' proper direction, shaft 45 and screw 68 are rotated so as to move adjusting member 64 outwardly toward the' closed end 58 ofy ove 59. This causes outward movement of blade 62, which, through the interengagement of oblique faces of cut out portions 58a and 62a of the respective parts, moves cylinder engagingelement 58 radially outwardly,

thereby posltioning the abrasive member 59 at a greater distance from the-axis ofrotation. When the knob 49 -is turned in theopposite direction, adjusting member 64 and blade 62 are retracted, thereby permitting cylinder-engaging element 58 to move radially inwardly. As the vribs 60 are formed integral with mandrel' 42, they are notA adjustable but they serve merely to-space the element -58 in proper position wlthin the bore. l.

A guard 7'1 is pivotally mounted at one end two spaced members forming driver disk 27.

A bar 75 is secured to guard 71 immediately in front of driver disk 27 and extends forwardly alongside the opposite side of driven disk 28.v Guard 71 and bar 75 prevent an o erators hand and his clothing, or other o jects, from being caught and drawn between said disks.

Shoe 58 is preferably held in slot 57 by the tension of a spring 77 which is secured in said slot to one side of blade 62 and bears against one end of said shoe, the other end of the latter being engaged by a shoulder 78 formed in said slot. Shoe 58 and abrasive stick 59 are adjustable radially of the mandrel to insure the desired finish of a bore.

In order to increase the range of usefulness of the device, and enable it to be used in honing bores of varying diameters, mandrel 42 is formed detachable from the hollow spindle 44. A plurality of mandrels 42 of varying diameters is provided so that a mandrel of proper size can be used. The attachment or removal of the mandrel can be quickly and easily made by the operation of coupling 52.

Supporting member l5 can be adjusted about the vertical axis of bolt 17 so as to present the mandrel 42 at any angle desired. It can be readily attached to and detached from the bench. einber 36 provides an easily detachable and flexible connection between the drill 38 and the driver spindle 26. The relative sizes of disks 27 and 28 can be varied to obtain the required speed of the mandrel.

When rock shaft 2l is rocked forwardly the spaced anges of driver disk 27 engage and grip therebetween the edge of driven disk 28 so that the mandrel 42 is positively driven by the drill 38 without the use of belts or other external transmission means.

When the driving mechanism, including drill 38, bearing 24 and driver disk 27, occupies disengaged position 4( shown in Figure 3), it is desirable to limit the outward movement thereof. To this end, a pair of spaced vertical lugs 79 is formed integral with casting 15 adjacent to bearings 20. Similar pair of lugs 80 is formed integral with bearing 22. Thus when member 24 is rocked away from member 15 lugs 79 engage lugs 8O and form a stop for member 24.

The mandrel 42 is preferably made of die cast metal containing zinc, aluminum and copper of such proportions as will give-the necessary strength and hardness in view of the fact that the lugs or guide elements 61, 61 are formed integrally with the mandrel and must be non-abrasive when operating in contact with the cylindrical wall of the hole being ground. In fact, one of the features of my invention is that but a single abrasive element 59 is used which makes it possible for the groove 57, in which the shoe 58 is mounted, to be of substantial depth so as to give a wide latitude of radial adjustment to the shoe and, of course, abrasive element 59 carried thereby. In order that the rotation of the abrasive element 59 may be confined to a definite orbit for grinding holes to a true cylindrical shape, there are two ribs 60 or guide elements spaced unequal distances radially from the abrasive element 59. The reason for the unequal spacing of the lugs 60, 60 is to provide a means of correcting (in some instances) the tendency to grind a noncylindrical hole. This correction may be accomplished by periodically reversing the relative positions of grinder and thing being ground. It is obvious that the two guide lugs together with the abrasive element give three point contact within the hole that is being ground so that it is necessary to adjust but one of these elements (preferably the grinding element 59) to maintain this three point contact for any size hole within the range of operation of the tool. This is axiomatic, as it is a fundamental law of mathematics'that a circle can be described through any three points not in a straight line. If the tool had more than three contact points it would be necessary to adjust more than one of the contacting points to adapt the tool to different sizes of cylindrical holes. If. the tool had only two contacting points it would not rotate on a fixed circular orbit, but would have a tendency to travel or creep producing a hole that would not be truly cylindrical.

By making the mandrel 42 of die cast metal having the proper composition so as to be of the correct degree of hardness with respect to the wall of the hole being ground the guide lugs 60, 60 may be cast integrally with the mandrel which greatly simplifies the construction of thc mandrel. The composition of the alloy from which the mandrel is made must be such that it will be non-abrasive with respect to the metal defining the hole being ground and it must not possess ductility, such that it will spread or draw out away from the main body of the mandrel. On the other hand, the lugs 60, 60 should be suiiciently friable so as to gradually wear down by attrition smoothly and evenly.

I claim:

1. A boiling machine comprising a stationary support, an electric hand drill detachably mounted on said support, a mandrel journaled ifi said support in spaced relation with said drill, said mandrel being provided with a longitudinally disposed groove and a plurality of longitudinally disposed ribs spaced peripherally from each other and from said groove, a longitudinally disposed blade movfabl mounted in said groove and having an obhquely disposed face, an abrasive stick carrying shoe disposed in said groove and 1n engagement with said oblique face whereby ribs spaced peripherally from said groove,

an abrasive stick 'shoe arranged in said groove, means associated with said mandrel for adjusting said shoe radially, a horizontally disposed rod loosely journaled in said support, a motor mounted on said rod, a driven member operatively associated with said mandrel, and a driver member associated with said motor and engageable with said driven member for actuating said mandrel, said motor being oscillatable about the axis of said rod to bring said driver member into and out of operative engagement with said driven member. f

3. A honing machine comprising a stationary support, a horizontally disposed mandrel journaled in said support and provided with a longitudinal groove and a plurallty of longitudinally disposed ribs spaced peripherally from said groove, a blade movably arranged in said groove and adjustable longitudinally thereof, an abrasive stickshoe disposed in said groove and cooperatively arranged with said blade whereby the longitudinal movement of the latter imparts radial movement to said shoe, said ribs forming non-abrasive points of engagement with the surface of a bore operated upon by the abrasive stick of said shoe, thereby insuring proper alignment of the article operated upon with said mandrel, a rock shaft mounted in said support in spaced relation with said revoluble member, a hand drill carried by said rock shaft and l adjustable'in a vertical and horizontal plane, 50-

a friction driver disk operatively associated with said drill, and a friction driven disk operatively associated with said mandrel and engageable by said driver disk, said drill and said driver disk being oscillatable on said' rock shaft so as to disengage said driver disk from said driven disk. p

4. A honing machine comprising a stationl ary support adapted to be secured to a bench tudinally thereof, an abrasive stick shoe disposed in said groove and cooperatively arranged with said blade whereby the longitudinal movement ofthe latter imparts radial movement to said shoe, said ribs forming non-abrasive points of engagement with the surface of a bore operated upon by the abrasive stick of said mount, thereby insuring proper alignment of the article operated upon with said mandrel, a rock shaft mounted in sald support in spaced relation with said mandrel, a handdrill carried by'said rock shaft, a bearing member carried by said rock shaft, a driver spindle j ournaled in said bearing member, a friction driver disk fixed to said driver spindle, and a friction driven disk operatively associated with said mandrel and engageable by said driver disk, said drill and said bearing member being oseillatable on said rock shaft so aslto disengage said driving disk from said driven disk.

5. A honing machine comprising a stationary support adapted to be secured to a bench v1se, a horizontally disposed mandrel journaled in said support and provided with a longitudinal groove and a plurality of longitudinally disposed ribs spaced peripherally from said groove, a blade movably arranged in said groove and adjustable longitudinally thereof, an abrasive stick shoe disposed in said .groove and cooperatively arranged with said blade whereby the longitudinal movement of the latter imparts radial movement to said shoe, said ribs forming non-abrasive oints of engagement with the surface of a ore'operated upon by the abrasive stick of said shoe, thereby insuring proper alignment of the article operated upon with said mandrel, a rock shaft mounted in said support in spaced relation with said mandrel, a hand drill carried by said rock shaft, a bearing member mounted on said rock shaft, a driver spindle journaled in said bearing member, a driver member fixed to said spindle, means for detachably connecting said spindle with said drill, a driven member operatively associated with said mandrel and engageable by said driver member, said rock shaft being oscillatable so as to disengage said driver disk from said driven disk, means cooperating with said drill for yieldably maintaining said member in disengaged relation, and a rock arm fixed to said bearing member and operable to move said rock shaft to interengage said driver and driven members and effect operation of said mandrel.

6.' A honing machine comprising a stationary support, a horizontally disposed mandrel journaled in said support and provided with a longitudinally disposed groove and a plurality of longitudinally disposed ribs spaced peripherally from said groove, a shoe arranged in said groove and extending radially therefrom, an yabrasive stick carried by said shoe, adjusting means in said mandrel and cooperatively engaging said shoe for adjusting the latter radially, said abrasive stick forming an abrasive cylinder engaging element and said ribs forming non-abrasive cylinder engaging elements, thereby causing the article operated upon to beheld in proper alignment with the tool, a horizontally disposed rock shaft journaled in said support in spaced relation with said mandrel, an electric drill mounted on one end of said rock shaft, a bearing member carried by said rock shaft, a friction driver wheel journaled in' said bearing and adapted to be operatively associated with said drill, a friction driven wheel in nonrotative relation with said mandrel, and a rock arni fixed to said bearing member and operable to rock said shaft and move said drill and said bearing member to interengage said disks.

f7. In a hole grinding machine, an elongated mandrel adapted for rotation in the hole to be ground, said mandrel having a 1ongitudinally disposed recess, an abrading element adjustably mounted in said recess, and a pair of longitudinally disposed guide elements formed integral with and projecting from the periphery of the mandrel in spaced relation with the abrading element and with each other. 4 ,X

8. In a hole grinding machine, an elongated mandrel adapted for rotation in the hole to be ground, said mandrel having a longitudinally disposed recess, an abrading' element adjustably mounted in said recess,

:and a pair of longitudinally disposed guide elements formed integral with and projecting from the periphery of the mandrel, said guide elements being in spaced relation and nonuniformly spaced from the abrading element.

9. In a hole grinding machine, a grinding tool comprising an elongated holder, an abrading element projecting radially from the holder .and extending longitudinally thereof, means for varying the extent of projection of the abrading element beyond the periphery of the holder, and twd spaced guide elements projecting in fixed position from the periphery of the holder and extending longitudinally thereof, thc abradingelement and the guide elements forming bearings for the Work. .1j v

10. In a hole grinding machine, an elongatedmandrel adapted for rotation in the hole to lie-ground, saidmandrel having a lon itudinally disposed recess, an abrading eI mentadjustably mounted 'in said recess, and a pair of longitudinally disposed guide elements formed integral with and projecting from the periphery of the mandrel, the guide element following the abrasive element with respect to the direction of rotation being closer to the abrasive element than the leading guide element.

11,vv In a hole grindin machine, a grinding tool comprisingv an e ongated holder, an abrading element projecting radially from the holder and extending longitudinally thereof, means for varying the extent of projection of the abrading element beyond the periphery of the holder without varying its position longitudinally of the holder, and two spaced guide elements projecting in fixed position from the periphery of the holder and extending longitudinally thereof substantially coextensive with the abrading element, said guide elements being relatively nonabrasive to the wall of the hole being ground.

12. In a hole grindin machine, a rinding tool comprising an e ongated ho der, an abrading element projecting radially from the holder and extending longitudinally thereof, means for varying the extent of projection of the abrading element beyond the periphery of the holder, and two spaced guide elements projecting from the periphery of the holder and extending longitudinally thereof coextensive with the abradin element, said guide elements being non-a justably'xed to the holder.

13. In a hole grindin machine, a grinding tool comprising an e ongated holder, an abrading element projecting radially from the holder and extending longitudinally thereof, means for varyin the extent of projection of the abrading e ement beyond the periphery of the holder, and two spaced guide elements yprojecting from the periphery of the holder and extending longitudinally thereof, said guide elements being non-adj ustably fixed to the holder and non-abrasive to the wall of the hole being ground, the abrading element and the bearings for the wor 14. In a hole grinding machine, a grinding tool comprising a mandrel adapted to contact with the wall of the hole along but three radiallyvspaced surfaces of comparatively narrow breadth one of said surfaces being an abrading surface and the other two non-abrading surfaces the abrading surface and the non-abradingV surfaces forming bearings for the work, and means for varying the position of one of said'surfaces with respect to the rotation axis of the mandrel to adjust the mandrel to different sizes of holes.

15. In a hole; grinding machine, a grindguide elements forming ying tool comprislng a mandrel adapted to contact with the wall of the hole along but three radially spaced surfaces of comparatively narrow breadth, one of said surfaces being an abrading surface and the other two non-abrading surfaces the abradingsurface and the non-abrading surfaces'formm bea-rings for the work, and means for varymg the position of the abradin to the rotation axis o? the mandrel to adjust the same to different sizes of holes.

16. In a hole grinding machine, a grinding tool comprising a mandrel adapted tacontact with the wall of the hole along three radially spaced surfaces of comparatively narsurface with respect 1 row'breadth, one of said surfaces being an abrading surface and the other two nonabradingv surfaces the abrading surface and the non-abrading surfaces forming bearings for the Work, and means for varying the position of one of said 'surfaces With respect to the rotation axis of the vmandrel While the positions of the other surfaces remain fixed to adjust the mandrel to difl'erent sizes of holes.

17. In a hole grinding machine, a grinding tool comprising a bar, adapted for rotation in the hole to be ground, an abrading element projecting from the periphery of the bar and extending longitudinally thereof, means for varying the position of the abrading elelnent with respect to the rotation aXis of the bar, and a pair of ribs projecting in spaced relation from the bar and spaced from the abrading element, said ribs cooperating to hold the abrading element on a circular orbit during the rotation of the bar in a hole.

18. In a hole grinding machine, an elongated mandrel adapted for rotation in the hole to be ground, said mandrel having a lonv gitudinally disposed recess, an abrading element adjustably mounted in said recess, and a pair of guide elements projecting from the periphery of the mandrel in spaced relation, said guide elements being composed of ma terial adapted to wear by attrition as the mandrel is rotated in the hole being ground.

19. In a hole grinding machine, an elongated mandrel adapted forrotation inthehole to be ground, said mandrel being formed of an alloy of zinc containing copper and aluminum and having a longitudinally disposed recess, an abrading element adjustably mounted in said recess, and a pair of guide elements projecting from the periphery of the. mandrel in spaced relation and formed integral therewith,`said guide elements being adapted to Wear by attrition as the mandrel is rotated in thel hole belng ground. A y

In testimony whereof I hereunto affix my signature this 23rd day of October, 1931.

JOSEPH SUN NEN. 

